This invention relates to a waveform measuring instrument having a resident programmed processor and particularly to a waveform memory unit for storage of digitized waveform data and having data modifying register apparatus.
Digital devices are employed in the measurement and analysis of changing physical phenomena which may be of a repetitive or transient nature. Generally, a transducer develops an analog voltage signal in accordance with a sensed physical phenomena. The transduced electrical signal is connected as the input to the digital device which includes means for digitizing the signal, storing such digitized signal in memory and reproducing a replica of the analog signal from which such digitized data. Various modes of signal acquisition and presentation are provided in recently developed digital devices.
A particularly satisfactory and improved waveform measuring and analyzing instrument incorporating all the characteristics of digital oscilloscopes and transient recorders and in addition unique signal processing capability is disclosed in the copending application of Frederick A. Rose entitled "WAVEFORM MEASURING MEANS WITH RESIDENT PROGRAMMED PROCESSOR FOR CONTROLLED WAVEFORM DISPLAY AND WAVEFORM DATA REDUCTION AND CALCULATION" filed on Mar. 26, 1976 bearing Ser. No. 670,703 and assigned to the same assignee. As more fully disclosed therein, a resident programmed processor in the instrument permits the user to execute various calculations upon the waveform data stored in a digital memory unit.
A digital memory unit generally includes a plurality of words of a selected bit width. The memory unit of a general purpose computer generally is a wide word memory with the data stored in floating point form. In waveform instruments of the prior art, relatively narrow word memories are employed with the data stored in fixed point form. A single modifying value may be provided as a multiplier. For example, a block multiplier register can be associated with the digital memory unit in waveform instruments and applied as an exponent to a block of the memory locations.
In the programmed processor based instrument of the above-identified application, the waveform data memory unit is a random access memory. For purposes of economy and compactness, the size of the waveform data memory unit is limited and a relatively narrow storage word used as a fixed point number is preferably employed for each data location. Where the waveform includes a large constant value, a great number of word bits are necessary to record such constant and the variable value is spread over a very few number of bits. Further, the resident calculation upon the waveform data, which occurs many times in conventional waveform analysis, may result in a loss of precision in the waveform data as the stored data is appropriately modified and remodified and then again stored in memory.